Learning about deliverability: 33 DELIVTERMS and counting

Way back in April, 2022, I started a new series here on Spam Resource: DELIVTERMS. 

The goal of this awkwardly-named exercise was to help to define deliverability terminology. Deliverability and email technology are notoriously overwhelmed with technobabble and innumerable, inscrutable acronyms that those of us in the space bandy about as though we’ve purchased them in ten packs for a dollar. I wanted to do what I can to help pierce that shield of non-understanding and make things for the average person to better understand.

This isn't a list of 50, or 500, or even 100 terms. So how did I decide which ones to focus on? It's easy; they're always a term or topic that somebody is asking me about at that given time. When I wrote about greylisting, I was consulting for a client who was running into it (among other issues). Catch-all domains? They're something that email verification systems run into quite often. Email authentication? It's a huge focus in my new job, and covers a lot of what I'm connecting with people about lately. And so on. So this really is almost a list of "the bits of deliverability I most often touch, have to deal with, or explain to others." Especially VERP. VERP was one of the first ones and I had felt like I have had to explain VERP to people at least a thousand times in my career so far. It's just not something that most people "get." Anyway. I digress.

Here's what I've defined so far. What other terms should I add to the list? Let me know, please!
  1. B2B and B2C (businesses sometimes talk to businesses, and sometimes to consumers)
  2. BIMI (or, as I like to call it, a brand avatar)
  3. Blocklist (or, lists of IPs and domains that made somebody mad)
  4. CAN-SPAM (America's somewhat useless spam law)
  5. CASL (or, why you can't spam in Canada)
  6. Catch-all (a special type of email address or collection bucket) 
  7. COI/DOI (or verifying addresses and consent to prevent spam issues) 
  8. Deliverability (the one term that covers every single thing I talk about on this blog)
  9. DMARC (the email authentication thing that really ties the room together)
  10. Domain Warming (or, building up your reputation for fun and profit)
  11. DomainKeys Identified Mail (DKIM) (the current standard domain email authentication)
  12. DNS aka Domain Name System (the phone book of the internet)
  13. Email Authentication (how we know email domains are really yours)
  14. Friendly From (or, the text that identifies you in a way that the address cannot)
  15. FQDN (something something, relating to domain names)
  16. Google Postmaster Tools (GPT) (Google's reputation portal)
  17. Greylisting (an annoying and mostly useless type of spam filtering)
  18. HELO/EHLO (or how to say hi to an SMTP server)
  19. ISP and MBP (Internet Service Providers and Mailbox Providers)
  20. ISP Feedback Loop (FBL) (how you learn about spam complaints)
  21. JMRP (Microsoft's ISP Feedback Loop)
  22. List-ID (a very useful email header)
  23. M3AAWG (Email/Anti-Abuse Industry Group)
  24. Microsoft Smart Network Data Services (SNDS) (Microsoft's reputation portal)
  25. MTA and MUA (Mail servers and mail clients)
  26. NDR (or why didn't your mail get delivered?)
  27. Postmaster Site (a very useful thing for deliverability people)
  28. PSL aka Public Suffix List (a magical thing that makes DMARC work properly)
  29. Return-path/Envelope sender (the domain/header used for bounce tracking)
  30. Spamhaus (the king of blocklist providers) 
  31. Sender Policy Framework (SPF) (mapping IPs to servers for email authentication)
  32. Variable Envelope Return Path/VERP (a way of encoding bounce addresses for better bounce tracking)
  33. VMC (The certificate a sender purchases when configuring BIMI)
And if you're reading this at some point in the future, you can head on over to the live topic tag for DELIVTERMS to see if I've added any new ones.

I'm not the only person looking to define deliverability-related concepts. Be sure to check out Jennifer Nespola Lantz's "ISKTBN: I should know this by now" blog for more scholarly deliverability insights.

And after starting my series, I later realized that Tony Patti had put together his own "Deliverability Acronyms" series, having had the idea to do this a few years before I did. eDataSource may have become Sparkpost which may have become Bird, but thankfully you can still find part one, part two, and part three of his definitions online. I've occasionally since used his list for inspiration for additional entries to flesh out my own series. Thank you for sharing this, Tony!

Do you prefer to time travel back further? There's the "Ultimate Email Glossary: 178 Common Terms Defined" courtesy of MarketingSherpa, dated July 29, 2004. (Thanks to Laura Atkins for that link.)


  1. Hey Al, when you ran out of ideas you can take a look at the glossary I put together years ago with about 500 Deliverability terms: https://topdeliverability.com/glossary/


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